The impact of mouse strain on iron ion radio-immune response of leukocyte populations

Abstract

Purpose: Exposure to various forms of radiation, including iron ions that have an exceptionally high biological effectiveness, is an inevitable consequence of spaceflight. However, genetic background can significantly influence the response to radiation and hence also the overall health of crewmembers. The major goal of this study was to compare leukocyte population responses in two strains of mice that differ in susceptibility to radiation: C57BL/6 (resistant) and CBA/Ca (susceptible).

Materials and methods: The mice were whole-body irradiated with 0, 50, 200, or 300 cGy ⁵⁶Fe²⁶ (1 GeV) at ∼1 Gy/min and euthanised on days 4 and 30 thereafter for analyses. Analyses included body and organ masses (spleen, liver, thymus, lungs), distribution of leukocyte populations in blood and spleen, red blood cell and platelet characteristics, expression of surface molecules (CD11b, CD54), and spontaneous and mitogen-induced blastogenesis.

Results: There were main effects of Dose and Dose × Day interactions on virtually all quantified parameters in both strains of mice. In contrast, there were relatively few Dose × Strain and three-way interactions. Strain-related interactions involved changes in circulating phagocytic populations, erythrocytes, and liver mass.

Conclusion: The data demonstrate that genetic background can modify certain immune-related parameters after exposure to heavy particle radiation. The possible implications of these findings are discussed.

Keywords:

• heavy particle radiation
• high-LET radiation
• immune system
• liver
• radiosensitivity

Acknowledgements

The authors thank Gregory A. Nelson, PhD, Radha Dutta-Roy, Anna L. Smith, Tamako A. Jones, Melba L. Andres, Glen M. Miller, Dong Won Kim, Judy Folz-Holbeck, Lora Benzatyan, Mauricio DosSantos, and Maritess G. Asumen for valuable technical assistance. In addition, the support of Marcelo Vazquez, PhD, Mary Ann Kershaw, Katheryn Conkling, and the AGS support staff at BNL, and the physics group from the Lawrence Berkeley Laboratory are greatly appreciated. This study was supported in part by the National Aeronautics and Space Administration (NASA NCC9-79), and the Department of Radiation Medicine of the Loma Linda University Medical Center.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.